Winds of Change: Navigating exoplanet atmospheres at high spectral resolution across spatial scales

Exoplanet atmospheres reveal complex dynamical and chemical processes at high spectral resolution. As one of the largest optical telescopes in the world to-date, the Large Binocular Telescope (LBT) is an ideal facility with the sensitivity to observe exoplanet atmospheres, and provides a first look into the science that will be accessible in the era of Extremely Large Telescopes (ELTs). We conduct high-resolution (R ∼ 130,000) transit spectroscopy of observationally favorable and phenomenologically intriguing ultra-hot Jupiter atmospheres (KELT-9 b, KELT-20 b, and WASP-12 b) using the PEPSI fiber-fed optical echelle spectrograph on the LBT. We investigate spectroscopic signatures of hydrostatic circulation and hydrodynamic escape in these extremely irradiated atmospheres, highlighting empirical nuances such as their three-dimensional inhomogeneities and potential temporal variability. Looking to the future, we explore an instrument concept called fiber nulling to enable direct spectroscopy of temperate-zone exoplanet atmospheres, with the ultimate goal of searching for molecular tracers of planet formation and potential biosignatures in broadband near-infrared light at high spectral resolution. We present a laboratory proof-of-concept of a dual-aperture fiber nuller in monochromatic optical light, demonstrating sub- λ/B angular sensitivity. Finally, we investigate transmissive pupil-plane mask technologies for cross-aperture nulling. We empirically demonstrate that a scalar vortex with a well-calibrated wedge and liquid crystal polymer phase knifes are viable technologies for achromatic fiber nulling with null depths 10⁻⁴. Collectively, these efforts help lay the groundwork for next-generation giant exoplanet science and technology development, broadening the reach of atmospheric characterization from ultra-hot Jupiters to temperate analogs of Solar System gas giants.